1. Field of the Invention
This invention relates, in general, to heat sinks and more particularly to an integrated alternator bridge heat sink that transfers heat directly to the alternator casting.
2. Background Art
Electronic devices such as diodes and transistors having substantially large currents flowing therethrough generate a large amount of heat that may cause the device to self destruct unless the heat is dissipated fairly rapidly from the device. Typically, heat sinks to which the devices are attached, are made of a light, thermally conductive metal such as aluminum and are "finned" in order to expose as much surface area as possible to the surrounding atmosphere.
A three phase alternator bridge, such as used in an automobile alternator, comprises three "negative" diodes having their anodes connected to a ground terminal and three "positive" diodes having their cathodes connected to a voltage terminal. Each of the cathodes of the "negative" diodes are connected to one of the anodes of the three "positive" diodes and to one of three stator windings of an alternator. One approach comprises connecting the three "negative" diodes to an intermediate heat sink made of a material such as copper, which in turn, is connected to a somewhat larger aluminum finned heat sink. The "positive" diodes are similarly connected to intermediate copper heat sinks and another aluminum heat sink in similar fashion. The heat from the diodes is transferred through the intermediate copper heat sink to the aluminum heat sink and by convection into the surrounding atmosphere. The bridge is attached to the interior of the alternator casting where ambient air temperatures may reach approximately 100.degree. C.
This method just described has a large thermal resistance from the diode to the finned heat sink, thereby decreasing the efficiency of the thermal transfer. Also, a large amount of material is required for the finned heat sink, thereby increasing manufacturing costs and reducing space within the alternator casting.
Therefore, what is needed is a heat sink having a reduced thermal resistance between the heat generating device and the apparatus for sinking the heat, and reduced size for lowering cost and space requirements.